The Twenty-Six Martyrs of Japan (Japanese: , Hepburn: Nihon Nijroku Seijin) were a group of Catholics who were executed by crucifixion on February 5, 1597, in Nagasaki, Japan. Their martyrdom is especially significant in the history of the Catholic Church in Japan.

A promising beginning to Catholic missions in Japan with perhaps as many as 300,000 Catholics by the end of the 16th century met complications from competition between the missionary groups, political difficulty between Portugal and Spain and factions within the government of Japan. Christianity was suppressed and it was during this time that the 26 martyrs were executed. By 1630, Catholicism had been driven underground. When Christian missionaries returned to Japan 250 years later, they found a community of "hidden Catholics" that had survived underground.

Kakure Kirishitan (Japanese: 隠れキリシタン, lit. '"hidden Christian"') is a modern term for a member of the Catholic Church in Japan that went underground at the start of the Edo period in the early 17th century due to Christianity's repression by the Tokugawa shogunate.